The present invention relates to fuel system valves, and particularly to a roll-over valve for closing a venting passageway in a vehicle fuel system if the vehicle is rolled over in an accident or tilted during breaking or cornering. More particularly, the present invention relates to a roll-over valve having a valve member equipped to counteract aerodynamic lifting forces applied to the valve member during discharge of fuel vapor through the venting passageway that might otherwise move the valve member to prematurely engage and seal an outlet orifice in the venting passageway without impeding movement of the valve member toward an outlet-closing position during vehicle rollover conditions.
Vehicle fuel systems are known to include pressure-relief roll-over valves that are mountable on either the fuel tank or the filler neck of the vehicle. These conventional roll-over valves are configured to permit fuel vapor to vent from the fuel tank when the vehicle is operating normally, and to prevent fuel from spilling from the fuel tank through the vent when the vehicle is tilted a preselected amount or is rolled over in an accident. Desirably, a roll-over valve should be equipped to accommodate a substantial flow rate of fuel vapor from the fuel tank because of the large size of many fuel tanks and also because of the volatility of many newer blends of fuel. One problem encountered with roll-over valves that are capable of venting a substantial amount of fuel vapor is that the outbound flow of fuel vapor over the distal tip of the valve stem can create a low pressure area that can impose a lifting force on the distal tip to seal an outlet orifice in the venting passageway prematurely. Such premature sealing of an outlet orifice within the valve is not desirable because it blocks venting of fuel vapor from the fuel tank during instances when venting would otherwise occur.
One object of the present invention is to provide a roll-over valve in which the valve member is configured to counteract lifting forces exerted on the distal tip resulting from the formation of a low pressure area above the valve member that could cause the distal tip to seal an outlet orifice in the valve prematurely.
Another object of the present invention is to provide a roll-over valve equipped to retain the valve member in its outlet-opening position until the valve member is actuated to move toward an outlet-closing position in response to tilting the valve member during vehicle rollover conditions.
Yet another object of the present invention is to provide a roll-over valve equipped to counteract movement-inducing effects of aerodynamic lift forces exerted on the distal tip of a valve member due to high fuel vapor flow conditions existing in a venturi passage between the distal tip and the outlet during discharge of fuel vapor through the outlet so that premature sealing engagement of the distal tip and the outlet is substantially prevented.
Still another object of the present invention is to provide a roll-over valve having a buoyant internal chamber sized to float the valve member in fuel displaced by the valve member during vehicle rollover conditions to exert buoyant forces on the valve member which neutralize lift-counteracting forces applied to the valve member, thereby permitting normal unimpeded movement of the valve member toward its outlet-closing position during a vehicle rollover conditions.
According to the present invention, a roll-over valve is provided for use in a vehicle fuel system having outlet means for discharging fuel vapor. The roll-over valve includes a hollow valve member, roll-over means for moving the hollow valve member from an outlet-opening position to an outlet-closing position in response to tilting the hollow valve member during vehicle rollover conditions, and anti-lift means in the hollow valve member for counteracting external aerodynamic forces exerted on the hollow valve member during discharge of fuel vapor through the outlet means.
In preferred embodiments, the anti-lift means is positioned in a region provided between the outlet means and the roll-over means in spaced-apart relation to the roll-over means. The anti-lift means include means for applying a downwardly-directed predetermined retaining force to the hollow valve member to aid in preventing premature upward movement of the hollow valve member toward closing engagement with the outlet means and means for neutralizing the predetermined retaining force during vehicle rollover conditions to permit normal unimpeded movement of the hollow valve member toward its outlet-closing position during operation of the roll-over means.
In preferred embodiments, the applying means includes at least one weighted member positioned within the interior of the buoyant container and movable therein. Desirably, the at least one weighted member has a predetermined mass selected to cause the magnitude of the downward predetermined retaining force to be substantially equivalent to the magnitude of the upward external aerodynamic forces.
Desirably, the neutralizing means includes a buoyant container having a volume selected to displace a predetermined amount of fuel in the vehicle fuel system during vehicle rollover conditions so that the buoyant container generates an upward buoyant force having a magnitude that is substantially equivalent to the magnitude of the downward predetermined retaining force.
The roll-over means desirably includes a movable roll-over ball member and at least one inclined ramp portion contacting the roll-over ball in camming relation. In operation, the roll-over ball rides on the at least one inclined ramp portion in a radially-outward direction in response to tilting of the hollow valve member to move the hollow valve member to its outlet-closing position. The applying means and the neutralizing means are configured to exert substantially equal and opposite forces on the roll-over means during vehicle roll-over conditions so that inertial movement of the roll-over ball in the radially-outward direction on the at least one inclined ramp portion due to inertia of the roll-over established during tilting of the hollow valve member is substantially unaffected by the downward predetermined retaining force provided by the at least one weighted member.
One feature of the present invention is provision of anti-lift means in the hollow valve member for continuously retaining the hollow valve member in its outlet-opening position until the hollow valve member is moved toward its outlet-closing position by the roll-over means. The anti-lift means normally operates to counteract movement-inducing effects of aerodynamic lift forces exerted on the distal tip of the valve member due to high fuel vapor flow conditions existing in the venturi passage during discharge of fuel vapor through the outlet means. Advantageously, premature sealing engagement of the distal tip and the outlet means is substantially prevented due to application of a downward retaining force generated by the weighted members on the hollow valve member.
Another feature of the present invention is the formation of hollow valve member to include a sealed buoyant chamber configured to float the hollow valve member in fuel displaced by the hollow valve member during vehicle rollover conditions. Advantageously, the buoyant chamber exerts a buoyant force on the hollow valve member which neutralizes the downward retaining force provided by the weighted members to permit normal unimpeded movement of the hollow valve member toward its outlet-closing position during operation of the roll-over means.
Another feature of the present invention is that the buoyant sealed interior chamber and the at least one weighted member are sized and shaped to exert substantially equal and opposite forces on the roll-over means during vehicle rollover conditions. In operation, movement of the roll-over ball in the radially-outward direction on the at least one inclined ramp portion due to its own inertia established during tilting of the hollow valve member will be substantially unaffected by the downward predetermined retaining force.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.